The necessity for providing sewage treatment plants to clean and purify water discharged from homes and factories is well known. The function of a sewage treatment facility is to receive raw sewage (water containing waste material) as discharged from a city sewerage system and clean it to ultimately produce purified water. This is accomplished through a series of biological and mechanical processes.
In a typical water treatment facility, the raw sewage is received from the sewerage system and passed through a coarse screen to remove large pieces of matter. The sewage is next directed to one or more primary sedimentation tanks or clarifiers. The sewage remains in primary sedimentation for a period of time sufficient to allow the majority of the heavy matter to settle to the bottom of the tank forming sludge. The sludge is removed for “digestion” by microorganisms. The digested sludge is dried and can be used as compost or fertilizer. The remaining liquid from this treatment is then aerated to remove ammonia and passed into final sedimentation water treatment tanks to remove any remaining solid material.
Water treatment tank configurations vary with each treatment facility application. This notwithstanding, most final sedimentation water treatment tanks are round. This simplifies automatic skimming, churning and/or bottom scraping operations. More specifically, by eliminating inaccessible corners and providing uniform surfaces a revolving arm or skimmer blade can provide complete and efficient collection and prevent sludge buildup.
During operation of one type of water treatment tank sediment containing water enters the center of the tank. In a continuous process, the lighter clean water is effectively decanted from the heavier sediment containing water. More particularly, the clean water is displaced from the tank by the constant flow of sediment containing water into the tank. The displaced clean water is forced to flow under a scum baffle plate for collecting floating scum and then over a weir, ultimately entering an effluent channel or launder. The launder directs the water to the next treatment stage where it is disinfected and further made safe to be discharged into a river or stream.
As is known in the art, the outdoor exposure of the water treatment tanks in direct sunlight encourages the growth of algae. This growth is most prevalent on the baffle, weir, spillway and launder. Disadvantageously, algae growth on these members inhibits the flow of clean water from the tank. Further, the algae can be carried in thick masses and high concentrations in the clean water being discharged from the final treatment tank. When this occurs, the plant experiences a spike in the total suspended solids reading which could create an EPA violation. Unfortunately, manually cleaning the components of the tank is a very labor intensive process.
U.S. Pat. No. 4,830,748 to Hall discloses an apparatus particularly useful for cleaning algae and other debris from a water treatment tank of the type described. More specifically, a series of brushes for cleaning the baffle, weir, spillway and launder are attached by means of a framework or bracket to the revolving skimmer blade of the round water treatment tank. As the skimmer blade is driven around the tank, these brushes sweep algae and other debris from the surfaces being cleaned.
While the apparatus disclosed in the Hall U.S. Pat. No. 4,830,748 is remarkably successful in cleaning algae and debris from a water treatment tank and has met with commercial success, further improvement of the apparatus is possible. More specifically, it is not unheard of for employees of a waste water treatment plan to inadvertently leave hoses, ladders or other equipment in the launder or along the spillway, weir or baffle after performing some service or function. In some instances, the brush cleaning system has been known to catch on and become entangled with these items as it passes. Under these circumstances the brush system including its series of support arms, framework and mounting bracket or even the revolving skimmer blade itself may become damaged. The present invention represents an improved apparatus for cleaning algae and other debris from a water treatment tank that substantially reduces or avoids potential damage as a result of this problem.